tests: add test demonstrating buggy path handling `hg debugupgraderepo` is currently buggy with regards to path handling when copying files in .hg/store/. Specifically, it applies the store filename encoding to paths instead of operating on raw files. This commit adds a test demonstrating the buggy behavior.

from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)